Braking device for thread-form material



Jan. 21, 1969 F. FRENGER 3,423,045

I BRAKING DEVICE FOR THREAD-FORM MATERIAL Filed Oct. 19, 1966 FIG?) 3 [17 {{ns g L fi il-"gnu gnu/2% FIG.4 6

INVENTOR FRIEDRICH FRENGER United States Patent M 7 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a braking device for threadform material comprising an elongated brake bar around which the thread is wound, means for drawing the thread from the bar, the bar lying at an acute angle to the path of the thread issuing from the bar, the bar having a free end and a mounting end, means mounting the bar at its mounting end for swinging movement to vary its angle relative to the path of the thread, and spring means urging the bar to swing in a direction to increase its angle relative to the path of the thread to thereby exert a braking effect on said thread-form material.

The invention relates to a braking device for threadform material drawn off from a supply, especially for synthetic threads drawn off from spinning bobbins on stretch twist machines.

Thread brakes which have the function of imparting a preliminary tension to the drawn-off thread and to feed it to the delivery mechanism are already known. In these known devices the thread braking is accomplished through friction of the thread on braking surfaces, for example by pressing of brake disks against the thread or by encircling friction on brake bars which are arranged perpendicularly to the direction of thread movement.

Although these thread brakes are generally adjustable, inasmuch as the contact pressure force or the number of turns around the brake bar or the angle of the turns on the bar can be varied, they are not capable of compensating for tension fluctuations in the drawn-oft thread. These tension fluctuations, which are caused largely by differing winding tensions in the production of the thread supply and by frictional differences in the thread drawoff dependent on the draw-01f point on the bobbin body, lead to a considerable impairment of quality of the finally treated threads. The tension fluctuations pass, after conduction of the thread over the thread brake, into the thread supplying mechanism and lead there to an alteration of the thread slip and thereby of the feed rate, whereby, in stretching at a constant stretching rate the effective stretching ratio changes. As a result of this there occur fluctuations of uniformity, strength and stretch in the stretched material, which are highly undesirable, especially in high-strength threads, for example tire cord.

In the twisting of thread-form material the tension fluctuations causing the slip in the supplying mechanism likewise have a bad effect, because in consequence of the fluctuations in the delivery speed the number of twist turns of the thread per unit of thread length vary at a constant spindle turning rate.

It is the primary object of the invention, in a thread brake with a brake bar encircled by the thread-form material, to balance the tension fluctuations in such a way that the thread runs into the supplying mechanism at a practically constant preliminary tension.

According to a feature of the invention this is accomplished by positioning the brake bar at an acute angle to the thread running direction and pivotally mounting it to swing against the force of a spring which acts in the direction of thread tautening.

Patented Jan. 21, 1969 In this arrangement there are on the brake bar, in consequence of its inclination, drawn-out thread turns, so that even slight swingings of the brake bar change the free running path between the thread supply and the supplying mechanism, whereby the tension fluctuations of the drawn-off thread manifesting themselves as fluctuations in length are virtually completely compensated for by swinging movements of the spring-influenced brake bar.

Expediently the arrangement is made in such a way that the brake bar is provided at a point .situated in the extension of the axis of the supply bobbin with an eye or the like, through which the thread is conducted in running onto the brake bar, the eye or the like being situated on the swinging axis of the brake bar. Thereby it is made certain that the thread, regardless of the run-off point shifting periodically on the thread supply bobbin always runs onto the brake bar at the same place.

In carrying out the invention, the swingability of the spring-loaded brake bar can be achieved by a bearing extension of the brake bar, which is bent preferably, at a right angle with respect to the brake bar, forming the eye, and is rotatably journaled in a stationary shell against the force of a torsion spring engaging, on the one hand, the shell and on the other hand, attached to the extension. In a preferred form of execution of the invention the rotary spring is a spiral spring surrounding the bearing extension.

In order to control large tension peaks by swinging of the brake bar, which may move the brake bar to a position close to the running direction of the thread running off from the brake bar, without pulling the thread off of the brake bar, the free end of the brake bar is bent over, so that the thread turns cannot slip off its end.

Further details of the invention will be more readily apparent from the following description when read in connection with the accompanying drawing in which:

FIG. 1 shows, in schematic front view, a multiplace stretch-twist machine equipped with the thread brake according to the invention;

FIG. 2 is a side view of a portion of the apparatus of FIG. 1;

FIG. 3 shows, on a larger scale, the thread brake represented partially in section; and

FIG. 4 is a detail view similar to FIG. 3, but with another spring arrangement.

As shown in FIG. 1 the thread 1 runs off from a supply bobbin 2 mounted on the stretch twist machine and, after passing through an eye 3, is wrapped several times, expediently two or three times around a brake bar 4, Whose lower end has a bend 5 as slip guard. The brake bar 4 is provided with a bearing extension 6, which is rotatably supported in a manner to be explained in detail below. After running off from the brake bar 4, the thread 1 goes to a delivery mechanism consisting of a traverse-motion thread distributor 7, a conduct pressure roller 8 and a driven delivery cylinder 9. After possibly passing over a stretching prong (not shown in the drawing) for a cold prestretch, the thread then reaches the stretching cylinder 10, which, for the achievement of the preliminary stretching, is driven at a greater circumferential velocity than the delivery cylinder 9. This stretching cylinder forms simultaneously the first cylinder of a second stretching field which the thread runs through, possibly after encircling another stretching prong (not shown in the drawing) for hot stretching. After the thread has been brought into contact in the second stretching field with a contact heating device 11, it runs onto the draw-off cylinder 12 which is driven at a higher circumferential velocity than the stretching cylinder 10. The stretched thread is then conducted through a thread guide 13 and by means of the twist ring 14 moved up and down is wound onto the driven twist spindle 15. With the exception of the thread brake, all of the stations described of the stretch twist machine are extremely well known and do not per se form any part of the present invention.

The bearing extension 6 of the brake bar 4 is, as is evident from FIGS. 3 and 4, rotatably supported in a stationarily mounted shell or tube 16. One end of a spiral spring 17 is connected to the sleeve 16 and the other end is fastened to a collar 18 fixed to the bearing extension 6. The extension 6 can be held in the shell 16 against axial shifting in any suitable manner, known per se. Swingings of the brake bar in the direction of the arrow 19 in FIG. 2 brings about a relieving of the spring 17, whose initial tension can be altered, for example, by alteration of one or both engagement points of the spring ends at the shell 16 and the collar 18. For this purpose, the shell and/or collar can be provided with bores distributed over their circumference for the reception of the spring ends. The fastening of the spring ends to shell and bearing extension can, of course, be carried out in any other suitable manner as well.

In the construction shown in FIG. 4, the spring 17 is replaced by a leaf spring or a torsion bar 20 mounted in the shell 16 which is fastened at one end to the shell and at its other end to the end of the bearing extension 6.

Instead of the spring arrangements described and represented in the drawing, obviously a large number of similarly acting spring forms are possible. For example, the bearing extension 6 can be provided with an arm arranged perpendicularly to it, at the end of which there is connected a draw spring or pressure spring. Further, it is possible, instead of a spring, to have a weight hung on this arm urging the brake rod 4 to turn in the direction of the arrow 19. Finally, the brake bar 4 does not necessarily have to be provided with a bearing extension 6 arranged at a right angle to it. The brake bar 4 can, on the contrary, also be extended coaxially beyond the eye 3 and there be connected with a spring, for example, a draw or pressure spiral spring, or also be connected to a bending spring clamped in place on one side, the brake bar 4 being borne in such a way that its eye 3 remains in its position on swinging, so that the thread path length remains preserved between the supply bobbin 2 and the eye 3.

From FIGS. 1 and 2 it becomes apparent that the thread drawn off from the bobbin 2 is subject, depending on whether it runs off from the beginning or end of the bobbin, to a differing friction on the bobbin body. If the thread runs off from the rear end, it slips over the whole bobbin body; but if it is drawn off from the front end of the bobbin it does not undergo any frictional impairment. This leads to periodic fluctuations which are controlled out by the swinging movements of the brake bar 4. In addition to these friction-caused tension fluctuations there may also be present tension fluctuations which arise from the production of the bobbins. These fluctuations in tension, too, are balanced out by the swinging movements described. Finally, the tension fluctuations caused in the drawn-off thread through the thread friction on the bobbin body depend in their magnitude and their period rate also on the diameter of the bobbin. When the spinning bobbin 2 is still full, the frictions are greater than in the case of the bobbin that is already very nearly unwound. Even these long-period fluctuations, however, no longer cause impairement of quality, because they, too, are compensated for by the thread brake according to the invention,

The use of the invention is not restricted to the stretch twist machine described 'here only by way of example. The thread brake according to the invention can be used in general successfully in the drawing off of thread-form material from bobbins or from cans, for the maintaining constant of the draw-off tension. In the case of drawing off from cans, fluctuations in tension result from the differing run-off lengths for the thread-form material. In the stretching of synthetic threads, fluctuations in tension in the drawing off have a still worse effect on the quality of the finished product than in the example described above if only one stretching field is provided.

While two embodiments of the invention have been shown and described it will be understood that these are illustrative only and are not to be taken as a definition of the scope of the invention, reference being had for this purpose to the appended claims.

What is claimed is:

1. A braking device for thread for-m material comprising an elongated brake bar around which the thread form material is wound, means for drawing the thread form material from the bar, the bar lying at an acute angle to the path of the thread drawn therefrom, the bar having a mounting end and a free end, means mounting the bar at its mounting end for swinging movement to vary its angle relative to the path of the thread form material, and spring means urging the bar to swing in a direction to increase its angle relative to the path of the thread form material to thereby exert a braking effect on said thread for-m material.

2. The braking device of claim 1 including an eye on the brake bar positioned substantially at the swinging axis thereof through which the thread form material passes before being wound around the bar.

3. The braking device of claim 1 in which the free end of the bar is formed with a rebent hook portion to prevent the thread form material from pulling off of the bar.

4. The braking device of claim 1 in which the bar is bent into a loop between its ends to define an eye through which the thread form material passes, the end portions of the bar lying at a right angle to each other and one end portion being journaled in a fixed shell.

5. The braking device of claim 4 in which the spring means is a coiled spring coiled around said one end portion secured thereto at one end and to the shell at its other end.

6. The braking device of claim 4 in which the shell has a bore into which said one end portion extends and the spring means is a torsion spring lying in the bore secured at one end to the shell and at its other end to said one end portion.

7. The braking device of claim 2 in which the thread form material is drawn from a cylindrical bobbin through the eye and the eye lies in an extension of the axis of the bobbin at one end thereof.

References Cited UNITED STATES PATENTS 957,507 5/1910 Hedge 242-1292 1,214,172 1/1917 Kinney 242-153 2,209,398 7/ 1940 Garrett 242-153 2,528,171 10/ 1950 Pehlivanian 242147 X 2,664,594 1/ 1954 Anderson 242147 X STANLEY N. GILREATH, Primary Examiner. 

